The virtual reality or teleexistence technology flourishes which provides real time telepresence where we have the illusion that we are really present and work in the virtual reality created by a computer or in the telereal world which actually exists in a very fine or hazardous environment. To make a human operator feel as if he or she were in that place, a high performance force display device is essential. In addition, it is necessary to conduct wide spectrum of research on the entire systems including sensors, actuators, and computer systems associated with the force display devices.
The following techniques are reported on the force display device used in the virtual reality system.
(1) M. Minsky, et al. disclose in ACM SIGGRAPH, Vol. 24,235, 1990, a "virtual sandpaper" that provides fingers with the surface texture of a virtual object. It has a sensor for detecting positions in all movable directions, and expresses texture by resistance created by a special big joy stick including motors and brakes, each of which is mounted on each shaft of the joy stick, thereby providing a hand with the surface texture of the virtual object. PA1 (2) Iwata, et al. disclose in ACM SIGGRAPH, vol. 24,165, 1990, a device that provides operator's fingers and hand with force senses through a special disk top manipulator when he or she touches a virtual object. The disk top manipulator has a configuration with many small, metal pantograph arranged ingeniously, and provides the force which is generated by a mechanism including motors to fingertips inserted thereto. PA1 (3) Hashimoto, et al. disclose in Journal of the Robotics Society of Japan, Vol. 10,903, 1992, a glove for analyzing the movement of a human hand. The glove is called a sensor glove driven by motors combined with wire transmission, and has three fingers and ten degrees of freedom. PA1 (4) Sato, et al. disclose in the Transactions of the Institute of Electronics, Information and Communication Engineers of Japan, D-2, Vol. 7,887, 1991, a technique which generates senses when touching an image on a display seen through a stereoscope by controlling tensions of a few wires connected to fingers using solenoids. PA1 (5) Hattori, in Rutgers University, discloses in "Artificial Reality World", Kogyo Tyosakai publishing company Ltd. 151, 1991, a technique for generating mechanical force when fingertips touch a virtual object, thereby providing the fingers with the sense as though the virtual object were actually present at the place. This device has micro cylinders mounted on thumb, index finger and middle finger, and a pump joined to the micro cylinders to supply air in real time, thereby generating push back forces on the fingers by supplying air pressure when the fingertips touch the virtual object. PA1 (6) Tanaka, et al. disclose in Japanese Patent Application Laid-open No. 6-507032/1994 (PCT/GB92/00729), and in Proceedings of the 71 JSME Spring Annual Meeting of the Japan Society of Mechanical Engineers, No. 4,373, 1994, a fluid glove which is worn on an operator's hand to provide force sense display. The fluid glove implements (tactile) operation sense corresponding to the grasp of a robot by controlling the pressure of the fluid (air). PA1 (1) German Patent DE3830836C2 discloses a technique which applies the electrorheological fluid to a power simulator of an airplane. It relates to a kind of servo support equipment for aiding muscular operations or preventing over actions as in the power steering of automobiles. PA1 (2) Ikeda, et al. discloses in the Proceedings of the 11-th Annual Conference of Robotics Society of Japan, 987, 1993, a technique which applies the electrorheological fluid to the output control of a biomimetic actuator. It relates to a controlling device of the mechanical output of artificial muscular.
Using the electrorheological fluid for controlling mechanical outputs is described in the following documents.
All the devices employing the electrorheological fluid relate to the control of mechanical outputs rather than the display of force senses, particularly the force display of the virtual reality system.
The foregoing conventional force display devices have various problems. For example, the devices using motors are large, limited in degrees of freedom, and inferior in response. The devices using solenoids or air cylinders have poor controllability, and difficulty in the display of delicate senses.